brucine

a white, crystalline, bitter, slightly water-soluble, very poisonous alkaloid, C 23 H 26 N 2 O 4 , obtained from the nux vomica tree Strychnos nux-vomica, and from other species of the same genus, resembling but not as powerful as strychnine in its pharmacological action: used chiefly in the denaturation of alcohol.